(1) Field of the Invention
The present invention relates generally to controlling the flow of a surrounding environmental fluid into an inlet formed in a moving vehicle, and more particularly to a system that uses vortices to control such a flow at the inlet of, for example, an underwater vehicle's underwater launch system.
(2) Description of the Prior Art
Many underwater launch systems used by underwater vehicles utilize the forward motion of the vehicle and underwater pressure to develop a dynamic pressure head for launch initiation. Briefly, an inlet formed in the vehicle's hull admits water as the vehicle moves forward. A launch pressurization system coupled to the inlet pressurizes and directs the water flow to a launch tube. The inlet can be open at all times or fitted with a door that is kept closed and flush with the vehicle's hull until a launch is required. For hydrodynamic reasons, the inlet door (if present) opens into the vehicle. However, an inlet that is open at all times or one having an inward-opening inlet door does not effectively direct the dynamic pressure of the moving water into the inlet. To increase the mass flow of fluid into such an inlet, the prior art has attempted to modify the door design or has positioned protuberances on the door or forward of the door.
Mohn (U.S. Pat. No. 4,174,083) discloses an ogee-shaped platform mounted on an air inlet door of an aircraft fuselage for generating a downwash of air into the inlet as the aircraft flies. In each embodiment, the platform remains in the airflow even when the inlet door is closed.
Mazzitelli (U.S. Pat. No. 4,696,442) discloses the use of two fixed-position vortex generators mounted forward of an aircraft's air inlet to generate a downwash of air into the inlet. The vortex generators remain in the airflow at all times.
The above-described prior art protuberance/vortex generator concepts are not suitable for an underwater vehicle as they generate hydrodynamic inefficiencies, an unwanted acoustic signature, and may not properly position the generated vortex relative to the inlet due to vehicle side slip motion and/or underwater currents.